'Dream' – Cardy created her own set of prompts for Inktober 2016. "I chose positive aspirational words. In this way the challenge became a personal, motivational and positive opportunity to grow and explore my creativity," Cardy told CNN.

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Photos:Inktober 2016

'A view in my little village' by Christine Rooney – UK artist Christine Rooney normally works with watercolor paints and oil, so Inktober allows her to do something different.

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Photos:Inktober 2016

'The Watcher' by Darcy Wilkinson – Wilkinson's bird drawing is her favorite Inktober sketch so far. The UK artist joined the challenge to use a medium she does not normally work with. She told CNN she is trying to work in a very loose sketch style to avoid worrying about mistakes.

"It was October when I challenged myself to draw in ink for every day of the month. The word ink just ended up fitting with it,"Parker told CNN.

As he shared his mission online, other artists decided to join in and make it an annual event. But it was only in 2012 that Inktober became a worldwide art celebrationas hashtags -- labels used on social media websites to join messages on a specific topic -- helped people spread the word and encourage others to join.

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There are more than 1,000,000 Inktober posts on Instagram. "Hashtags have been a tremendous help. The challenge's popularity definitely opened my mind to the possibilities of challenges that help creative communities," said Parker.

Being unable to edit his ink work has been one of the biggest challenges, he said.

"You cannot undo anything when working with ink on paper. But most of all it is hard to keep inspired. I want to tell beautiful stories, but good ideas don't always come daily so an endless drawing can be hard," Diez told CNN.

A splash of color

Many artists add their own creative twist to Inktober.

Welsh artist Kat Cardy likes to add a splash of color to all of her designs.

Welsh artist Kat Cardy created her own set of prompts for Inktober. Words like 'Protect' are used to inspire herself and others.

"I have used the challenge to practice inking, but I also wanted to make it my own. I'm a very moved by color, and my inked pieces always feel unfinished until they're colored, " Cardy told CNN.

Adding the color has been her favorite part of the process.

"The most important thing is that you have fun and enjoy the process, so don't stress too much about what others are doing," she said.